Fiber optic distribution cables and structures therefore

ABSTRACT

Fiber optic distribution cables and methods for manufacturing the same are disclosed. The fiber optic distribution cables present one or more optical fibers outward of the protective covering for distribution of the same toward the subscriber. In one fiber optic distribution cable, a length of distribution optical fiber that is removed from the distribution cable and presented outward of the protective covering is longer than the opening at access location. In another embodiment, a demarcation point is provided for inhibiting the movement (i.e., pistoning) of the distribution optical fiber into and out of the distribution cable. In still another embodiment, an indexing tube is provided for indexing a tether tube within the indexing tube for providing the distribution optical fiber with a suitable excess fiber length. Additionally, other embodiments may include a fiber optic distribution cable having a dry construction and/or a non-round cross-section.

RELATED APPLICATIONS

The present application is related to U.S. patent application Ser. No.11/432,637 titled “Tools and Methods for Manufacturing Fiber OpticDistribution Cables”, U.S. patent application Ser. No. 11/432,311 titled“Methods for Manufacturing Fiber Optic Distribution Cables”; and U.S.patent application Ser. No. 11/432,654 titled “Kits of Parts forManufacturing Fiber Optic Distribution Cables” all filed on even dateherewith, the disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to fiber optic distributioncables, methods for manufacturing the same, tools, and kits therefor.More particularly, the present invention relates to fiber opticdistribution cables, methods of manufacturing the same, tools, and kitsfor distributing optical fibers toward subscribers such as in opticalfiber to the home or curb applications (FTTx).

BACKGROUND OF THE INVENTION

Communication networks are used to transport a variety of signals suchas voice, video, data transmission, and the like. Traditionalcommunication networks use copper wires in cables for transportinginformation and data. However, copper cables have drawbacks because theyare large, heavy, and can only transmit a relatively limited amount ofdata with a reasonable cable diameter. Consequently, optical fibercables replaced most of the copper cables in long-haul communicationnetwork links, thereby providing greater bandwidth capacity forlong-haul links. However, most communication networks still use coppercables for distribution and/or drop links on the subscriber side of thecentral office. In other words, subscribers have a limited amount ofavailable bandwidth due to the constraints of copper cables in thecommunication network. Stated another way, the copper cables are abottleneck that inhibit the subscriber from fully utilizing therelatively high-bandwidth capacity of the optical fiber long-haulslinks.

As optical fibers are deployed deeper into communication networks,subscribers will have access to increased bandwidth. But certainobstacles exist that make it challenging and/or expensive to distributeoptical fibers toward the subscriber from fiber optic cables. By way ofexample, one conventional method for accessing optical fibers fordistribution from a fiber optic cable requires making a relatively longbreach in the cable jacket for accessing a suitable length of opticalfiber. FIG. 1 depicts a fiber optic cable 10 having a breach B in thecable jacket with a breach length BL. Breach length BL depends on thelength of an optical fiber OF required by the craft for the accessprocedure. By way of example, if the craftsman required 30 centimetersof distribution optical fiber OF for the access procedure, then breachlength BL has a slightly longer length such as 35 centimeters forpresenting 30 centimeters of optical fiber OF outside the cable jacket.More specifically, the optical fiber desired for distribution isselected and cut near the downstream end of breach B and then arrangedto exit the fiber optic cable near the upstream end of breach B, therebygiving the craftsman optical fiber OF with the required length. Onedrawback for this method is that the breach length BL is relatively longand disrupts the protection provided by the cable jacket. Stated anotherway, breach B must be closed and/or sealed in order to provide properprotection, which requires a relatively large covering that is bulky,cumbersome, and/or stiff. Consequently, the distribution fiber opticcable is too large and/or stiff at the distribution location, therebymaking effective routing of the distribution fiber optic cable throughsheeves, ducts, or the like during installation difficult, if notimpossible.

Another conventional method for accessing optical fibers fordistribution from a fiber optic cable requires breaching the cablejacket in two locations as shown in FIG. 2. FIG. 2 depicts a fiber opticcable 10′ with a first cable jacket breach B1 and a second (i.e.,downstream) cable jacket breach B2 that are spaced apart by asignificant distance D. By way of example, a typical distance D betweencable jacket breaches B1,B2 is about thirty centimeters. Then, theoptical fiber OF desired for distribution toward the subscriber isselected and cut at the location of the second cable jacket breach B2.Thereafter, the optical fiber OF that was cut at the second cable jacketbreach B2 is then located at first cable jacket breach B1 and thenpulled toward the first cable jacket breach B1 until it protrudestherefrom as shown. Simply stated, optical fiber OF for distributionmust be located twice (once at each jacket breach B1,B2) and the lengthof optical fiber OF protruding from the first cable jacket breach B1 isdependent on distance D between cable jacket breaches B1,B2. Typically,the cable jacket breaches B1,B2 are closed for providing environmentalprotection such as by overmolding or using a heat shrink tubing. Thus,this conventional procedure for accessing and presenting optical fibersfor distribution is time consuming, may damage the optical fibers,and/or creates a relatively large protrusion after sealing the cablejacket breaches.

Consequently, it would be desirable for distribution fiber optic cablesto have low-cost solutions that are craft-friendly for installation.Moreover, solutions should also offer relatively small-footprints,flexible distribution locations, easy servicing/repair, and/orversatility for connectivity. Additionally, the reliability androbustness of the distribution fiber optic cable assembly may have towithstand the rigors of an outdoor environment. The present inventionprovides reliable and low-cost solutions that are craft-friendly fordistributing optical fibers toward the subscriber from a fiber opticcable with a relatively small and flexible distribution location.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to a fiber opticdistribution cable for routing optical fibers toward the subscriber. Thefiber optic distribution cable includes a plurality of optical fiberswithin a protective covering and a distribution optical fiber. Thedistribution optical fiber is one of the plurality of optical fibers ofthe fiber optic distribution cable that is presented outward of theprotective covering at an access location for distribution toward thesubscriber. The access location has a length AL and the distributionoptical fiber removed from the fiber optic distribution cable has adistribution optical fiber length DOFL, wherein the distribution opticalfiber length is about 5/4 AL or more.

Another aspect of the present invention is directed to a fiber opticdistribution cable including a plurality of optical fibers, a protectivecovering, a distribution optical fiber, and a demarcation point. Thedistribution optical fiber being one of the plurality of optical fibersof the fiber optic distribution cable that is presented outward of theprotective covering at an access location. The demarcation point beingdisposed about a portion of the distribution optical fiber forinhibiting the movement of the distribution optical fiber. In otherwords, the demarcation point inhibits the distribution optical fiberfrom pistoning into or out of the fiber optic distribution cable.

Yet another aspect of the present invention is directed to a fiber opticdistribution cable including a plurality of optical fibers, a protectivecovering at least one distribution optical fiber, an indexing tube, anda tether tube. The at least one distribution optical fiber is selectedfrom one of optical fibers of the fiber optic distribution cable andprotrudes from an access location of the protective covering. The tethertube is disposed about a portion of the at least one distributionoptical fiber for protecting the at least one distribution opticalfiber. Also, the tether tube is attached at a predetermined positionrelative to the indexing tube, thereby loading an excess fiber length inthe distribution optical fiber. Additionally, other steps which may ormay not require other components can be performed on the fiber opticdistribution cables by the craft. For instance, a transition tube may beslid over the distribution optical fiber for protecting the same.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments of the invention,and are intended to provide an overview or framework for understandingthe nature and character of the invention as it is claimed. Theaccompanying drawings are included to provide a further understanding ofthe invention, and are incorporated into and constitute a part of thisspecification. The drawings illustrate various embodiments of theinvention, and together with the description serve to explain theprincipals and operations of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional method for opening afiber optic cable over a relatively large length to access a suitablelength of optical fiber for distribution of the same.

FIG. 2 is a perspective view of another conventional method for openinga fiber optic cable in two locations to access a suitable length ofoptical fiber for distribution of the same.

FIG. 3 is a perspective view of a generic fiber optic distribution cableshowing a distribution optical fiber protruding from a first accesslocation of a fiber optic distribution cable after being severed at acutting location within the fiber optic distribution cable according tothe present invention.

FIGS. 3 a-3 g are cross-sectional views of exemplary fiber opticdistribution cables that are represented by the generic fiber opticdistribution cable of FIG. 3.

FIG. 4 is a flowchart showing the steps of the method for making thefiber optic distribution cable of FIG. 3 according to the presentinvention.

FIGS. 5 and 5 a-5 f are respectively are perspective views of anexplanatory tool and variations on the explanatory tool for severing anoptical fiber within a fiber optic distribution cable according to thepresent invention.

FIG. 6 a depicts the tool of FIG. 5 with the cutting element loopedabout a plurality of distribution optical fibers of the fiber opticdistribution cable of FIG. 3 before severing.

FIG. 6 b depicts the tool of FIG. 5 inserted within the fiber opticdistribution cable of FIG. 3 for severing the distribution optical fiberat the cutting location within the fiber optic distribution cable.

FIG. 6 c depicts the fiber optic distribution cable of FIG. 3 along withan exploded view of a kit of parts according to the present invention.

FIG. 6 d is a cross-sectional view of the cap of FIG. 6 c.

FIG. 6 e is a perspective view of the fiber optic distribution cable ofFIG. 3 along with a kit of parts of FIG. 6 c assembled thereon accordingto the present invention.

FIG. 6 f depicts the assembly of FIG. 6 e after the cap is secured usinga suitable material.

FIG. 6 g depicts the tool of FIG. 5 positioned about a portion of afiber optic ribbon for splitting the optical fiber ribbon along itslength before severing the distribution optical fibers at the cuttinglocation.

FIG. 6 h is a perspective view of the fiber optic distribution cable ofFIG. 3 with an alternative cap configuration according to the presentinvention.

FIG. 6 i is another fiber optic distribution cable having a demarcationpoint disposed about the distribution optical fiber according to thepresent invention.

FIG. 7 is a side view of a fiber optic distribution cable assemblyaccording to the present invention.

FIG. 8 is an exploded view of the fiber optic distribution cableassembly of FIG. 7 according to the present invention.

FIG. 9 is a cross-sectional view of the fiber optic distribution cableassembly of FIG. 7 taken along line 9-9.

FIG. 10 is another cross-sectional view of the fiber optic distributionassembly cable of FIG. 7 taken along line 10-10 and FIG. 10 a is a viewof a portion of the cross-sectional view of FIG. 10.

FIG. 11 is another cross-sectional view of the fiber optic distributionassembly cable of FIG. 7 taken along line 11-11.

FIGS. 12-16 are perspective views showing portions of the distributioncable assembly of FIG. 7 in various stages of construction.

FIG. 17 is a perspective view of yet another fiber optic distributioncable that includes a ferrule according to the present invention.

FIG. 18 is a perspective view of the distribution cable of FIG. 17 witha portion of the overmold removed for clarity.

FIG. 19 is a perspective view of a tether tube having a preconnectorizedplug attached thereto for plug and play connectivity according to thepresent invention.

FIG. 19 a is a perspective view of a ferrule attached to a distributionoptical fiber according to the present invention.

FIGS. 19 b-19 e are perspective views of assemblies for plug andconnectivity according to the present invention.

FIG. 20 is a perspective view of an alternative sealing portionaccording to the present invention.

FIGS. 20 a-20 c are perspective views of an alternative fiber opticdistribution cable according to the present invention.

FIG. 21 is a side view of a fiber optic distribution cable having asafety pulling device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Whenever possible, the same reference numeralswill be used throughout the drawings to refer to the same or like parts.The present invention discloses distribution fiber optic cables andmethods of making the same where one or more optical fibers of a fiberoptic cable are presented outside a protective covering such as a cablejacket for distribution. Additionally, the present invention alsodiscloses tools for the methods of making along with kits of partsuseful for making the distribution fiber optic cables. In oneembodiment, a relatively small opening is formed at the access locationof the fiber optic cable, thereby leaving a relatively small accessfootprint (i.e., removing a small portion of the protective coveringand/or other cable components) on the fiber optic cable. Even though arelatively small opening is made at the access location (e.g., cablejacket breach), the method advantageously provides a length ofdistribution optical fiber protruding from the access location that islonger than the opening of the access location. By way of example, ifthe opening in the cable jacket is about 2 centimeters the distributionoptical fiber is cut within the distribution cable and has a length ofabout 2.5 centimeters or more. In other words, the craft has a suitablelength of distribution optical fiber to work with for distribution,while only having to manage one relatively small opening or breach inthe protective covering per access location. Unlike the conventionalaccess methods, this embodiment of the present invention does notrequire: (1) multiple cable breaches for a single access location; or(2) a relatively long cable jacket breach or opening that is about aslong as the length of distribution optical fiber. Consequently, theconventional access methods result in stiff, bulky, and relatively largedistribution footprints after reclosing or sealing the access locationfor protection. Whereas the length and/or cross-sectional area of accesslocations for fiber optic distribution cables of the present inventionare relatively small and flexible, thereby overcoming the problems ofthe conventional methods for accessing fiber optic cables to provide asuitable length of distribution optical fiber outward of the protectivecovering. However, certain aspects of the present invention may bepracticed with more than one cable breach or other aspects of theconventional methods.

FIG. 3 shows a perspective view of a generic distribution fiber opticcable 30 (hereinafter distribution cable 30) according to the presentinvention. Distribution cable 30 depicts a distribution optical fiber 32protruding from a first access location 38 a in a protective covering 38such as a cable jacket. As depicted, first access location 38 a has anaccess length AL, which is the length of the opening or breach inprotective covering 38. Additionally, distribution optical fiber 32 hasa distribution optical fiber length DOFL that is about 5/4 times theaccess length AL or longer and more preferably about 3/2 times theaccess length AL or longer. In other words, distribution optical fiber32 was cut or severed at a cutting location CL within distribution cable30. Illustratively, if the access length AL is 5 centimeters (i.e., theopening or breach of protective covering 38 at first access location 38a), then distribution optical fiber 32 has a distribution optical fiberlength DOFL of about 6 centimeters or longer and more preferably about7.5 centimeters or longer. Simply stated, the distribution optical fiberlength DOFL is greater than the access length AL of the first accesslocation 38 a since the distribution optical fiber is cut from withinthe fiber optic cable. Thus, the present invention provides the craftwith a suitable length of distribution optical fiber while using arelatively small opening or breach in the protective covering, therebyallowing a relatively small footprint for the distribution configurationselected. Of course, cable 30 may have any suitable number ofdistribution optical fibers 32 protruding from first access location 38a. Likewise, fiber optic distribution cables can have any suitablenumber of access locations disposed along the cable as desired. Fiberoptic distribution cables of the present invention may also use one ormore different methods and/or components for constructing the fiberoptic distribution cable based on the type of fiber optic cable selectedand type of connectivity desired.

Distribution cable 30 is generic since it represents fiber optic cablesthat allow cutting of the distribution optical fiber within theprotective covering according to the present invention. Illustratively,FIGS. 3 a-3 g depict a sampling of fiber optic cable constructions thatare useful according to the present invention. Respectively FIGS. 3 a-3g depict: a stranded loose tube cable (FIG. 3 a); a slotted core cable(FIG. 3 b); a monotube cable (FIG. 3 c); a flat ribbon cable (FIG. 3 d);an indoor cable (FIG. 3 e); a cable having a plurality of tubes lashedtogether (FIG. 3 f); and a cable having bundles (FIG. 3 g). Simplystated, distribution cable 30 can have any suitable construction.Additionally, the present invention works with optical fibers of thedifferent cables types such as a plurality of optical fiber ribbons,loose optical fibers, buffered optical fibers, bundles of optical fibersor the like.

FIG. 4 depicts a flowchart 40 of a method for manufacturing adistribution cable using the concepts of the present invention. First, astep 41 of providing a distribution cable such as distribution cable 30having a plurality of optical fibers (not visible) and a protectivecovering such as a cable jacket is required. Next, a step 43 of makingan opening (i.e., opening or breaching the protective covering) in thedistribution cable at a first access location is performed for accessingone or more of the plurality of optical fibers within the distributioncable. More specifically, the protective covering is opened at the firstaccess location with an access length AL that is sufficient forpracticing the method disclosed herein. One reason this method of thepresent invention is advantageous over prior distribution methods isthat it only requires one relatively small opening per access location.Moreover, depending on the construction of the distribution cableselected, other cable components, or portions thereof, may require beingcut, opened, and/or removed for accessing the desired optical fiberswithin the distribution cable. For instance, the craftsman may have toremove or cut away a portion of a water-swellable tape, armor, strengthmembers or the like for gaining access to the plurality of opticalfibers within the distribution cable. Thereafter, method 40 requires astep 45 of selecting at least one of the plurality of optical fibers ofthe distribution cable as a distribution optical fiber.

Then the craft performs a step 47 of cutting (i.e., severing) thedistribution optical fiber 32 at a cutting location within thedistribution cable at a downstream location. As used herein, a cuttinglocation within the distribution cable means a location along thedistribution cable where the protective covering is not breached. Asbest shown in FIGS. 6 a and 6 b, the step of cutting is performed bypositioning and inserting a suitable cutting tool within thedistribution cable, thereby allowing the tool to cut one or moredistribution optical fibers at the cutting location within thedistribution cable. Thereafter, a step 49 of routing the distributionoptical fiber through the opening at the first access location so that aportion of the distribution optical fiber is disposed outside theprotective covering is performed. Other optional steps are also possibleafter the distribution optical fiber is presented outside the protectivecovering. For instance, the distribution cable can optionally includeother steps and/or components such as providing a demarcation point, atransition tube, or components suitable for optical connectivity.

The method of flowchart 40 is useful for either factory or fieldapplications because it is simple, reliable, and craft-friendly.Illustratively, the method of flowchart 40 only requires one accesslocation opening per distribution location and the distribution opticalfiber length DOFL presented at the access location that is longer thanthe length of the cable breach or opening. Other methods may include oneor more optional steps such as providing other components and/or othersteps. More specifically, the method may further include one or more ofthe steps such as: providing a transition tube for routing thedistribution optical fiber (FIG. 6 c); providing a cap for closing thefirst access location (FIG. 6 c); providing a demarcation point aboutthe distribution optical fiber (FIG. 6 i); providing a tether tube aboutthe distribution optical fiber (FIG. 10); providing a plug (FIG. 10 a)for the index tube and/or tether tube; sealing the first access location(FIG. 14); providing an indexing tube for creating excess fiber lengthor excess ribbon length in the distribution optical fiber(s) (FIG. 15);and/or attaching a ferrule, a connector body, or the like (FIGS. 17 and18). Furthermore, a kit of parts as disclosed herein is useful forpracticing the methods and/or constructing the distribution cables ofthe present invention.

FIG. 5 depicts an explanatory tool 50 for severing one or moredistribution optical fibers within the distribution cable according tothe invention. Tool 50 has an elongate body 52 having a first end 54with an opening 56 and a cutting element 58. Cutting element 58 isflexible for fitting into opening 56 and is able to move through opening56 when pulled, thereby severing or cutting one or more distributionoptical fibers at the cutting location within the distribution cable.More specifically, pulling cutting element 58 causes the optical fiberscaptured by cutting element 58 to bend beyond their ultimate bendingradii so that they are severed or cut. As best shown by FIG. 6 a,cutting element 58 is looped about one or more distribution opticalfibers and both ends 58 a,58 b of cutting element 58 are routed throughopening 56 and positioned toward a second end 55 of tool 50 that is bentupward, thereby forming a handle for the operator. Thereafter, tool 50can be slid into the distribution cable to the desired cutting location(i.e., the loop in the cutting element is adjacent to the cuttinglocation) and then both ends 58 a,58 b of cutting element 58 are pulleduntil one or more distribution optical fibers within the distributioncable are severed. Consequently, the distribution optical fiber lengthDOFL has a length that is greater than the breach in the protectivecovering because the distribution optical fiber is cut within thedistribution cable.

Cutting element 58 requires certain characteristics for cutting orsevering one or more distribution optical fibers. For example, cuttingelement 58 must have the necessary strength for severing thedistribution optical fiber without breaking when pulled and theflexibility for looping into the at least one opening of the elongatebody while moving through the at least one opening when pulled. Cuttingelement 58 can use any suitable structure, size, shape, and/or materialfor meeting these requirements. Examples include structures such as oneor more filaments, threads, rovings, or yarns and examples of shapesinclude round, rectangular, and the like. In one embodiment, cuttingelement 58 is a aramid material such as Kevlar having a denier of about2450. However, cutting element 58 may be formed from other suitablematerials such as polymer material such as polyester or nylon, fishingline, a metallic material such as a steel wire, a cotton material, orthe like. For instance, one embodiment may use fifty pound test fishingline such as sold under the tradename SpiderWire®.

Likewise, elongate body 52 may be formed from any suitable material suchas metal or plastic that allow suitable dimensions for fitting withinthe selected distribution cable and yet remain somewhat flexible whilehaving the necessary strength. As depicted in FIG. 5 a, elongate body 52is formed from steel tape having a tool height TH of about 2 millimetersor less and a tool width TW of about 8 millimeters or less, therebymaking it flexible in one direction. As shown, opening 56 has agenerally rectangular shape with a length of about 5 millimeters and awidth of about 2 millimeters, but opening 56 can have other suitablesizes and/or shapes. Of course, the size and shape of the elongate bodycan be tailored for the size and shape of the space of the distributioncable that the tool must fit within such as rectangular or round. Forinstance, a tool with an arcuate-shape or rod-shape may be better suitedfor sliding into a round buffer tube. Additionally, other variations oftool 50 are contemplated by the present invention.

FIGS. 5 b-5 f depict variations on the explanatory tool according to theinvention. FIG. 5 b depicts a portion of a tool 50 b that has aplurality of openings 56 b near the first end. As depicted, tool 50 bhas three openings 56 b so the location of cutting element 58 may bevaried across the width of tool 50 b. FIG. 5 c depicts a portion of tool50 c having an opening 56 c that is non-round and larger for easilypassing the ends of the cutting element therethrough and guiding thecutting element when pulled. Likewise, the opening of the tool need notclose on itself. For instance, FIGS. 5 d and 5 e respectively depictportions of tools 50 d and 50 e where the openings 56 d,56 e are incommunication with the outer edge of the tool, thereby making theinsertion of cutting element 58 into the tools easier. FIG. 5 f depictstool 50 f having a handle 57 f having a movable portion 59 f for pullingcutting element 58 in order to severe one or more distribution opticalfibers. As shown, both ends 58 a,58 b of cutting element 58 are wrappedabout a protrusion (not numbered) of moveable portion 59 f of handle 57f so when it is actuated movable portion 59 f pulls in the directionshown by the arrow, thereby pulling on both ends 58 a, 58 b of cuttingelement 58 to cut the distribution optical fiber. Of course, other toolvariations are possible for pulling, wrapping, routing, mounting, orotherwise altering the tools disclosed for severing the distributionoptical fiber.

FIGS. 6 a and 6 b depict the use of tool 50 with distribution cable 30of FIG. 3. More specifically, FIG. 6 a shows distribution cable 30 afterthe opening is made at the first access location and one or more opticalfibers are selected as the distribution optical fibers. As furthershown, cutting element 58 of tool 50 looped is about the plurality ofdistribution optical fibers 32 that were selected. Stated another way,tool 50 and its cutting element 58 are positioned to cut a plurality theoptical fibers that are captured by the loop of the cutting element 58.Additionally, both ends 58 a,58 b of cutting element 58 are moved towardthe second end 55 of tool 50 and cutting element 58 is snugged-up aboutdistribution optical fibers 32. Thereafter, tool 50 is inserted withindistribution cable 30 and slid into a downstream location (e.g., awayfrom the head end of distribution cable). FIG. 6 b illustrates tool 50inserted within distribution cable 30 for severing a plurality ofdistribution optical fibers at cutting location CL. Thereafter, ends 58a,58 b of cutting element 58 are pulled with a force sufficient tosevere the distribution optical fibers 32 disposed between the loop ofcutting element 58 and elongate body 52. After tool 50 is removed fromwithin the distribution cable 30, the distribution optical fibers 32that are severed within the distribution cable 30 are routed through theopening at the first access location 38 a so that a portion of thedistribution optical fiber is routed outside protective covering 38 asshown in FIG. 3. From this point, distribution cables of the presentinvention may further include other manufacturing steps and/or othercomponents for making other assemblies of the present invention such assplicing to the distribution optical fiber and/or attaching a ferrule tothe distribution optical fiber.

For instance, FIG. 6 c shows distribution cable 30 of FIG. 3 along witha kit of parts 60 for closing first access location 38 a and routing thedistribution optical fibers 32 outside protective covering 38. Morespecifically, kit of parts 60 includes a transition tube 62 for routingand protecting distribution optical fibers 32 outside of protectivecovering 38 and a cap 64 for closing first access location 38 a andshielding the other optical fibers within the distribution cable. Inthis embodiment, the transition tube allows limited movement of thedistribution optical fiber into and out of the distribution cable (i.e.,allows pistoning) when it is bent. Generally speaking, the transitiontube allows the distribution optical fiber to have a pass-throughconstruction permitting limited movement of the same using thetransition tube as a pass-through conduit. In other embodiments, ademacaration point is disposed about the distribution optical fiber ator near the access location, thereby generally inhibiting the pistoningof the same into and out of the distribution cable. The use of thepass-through construction or demarcation point construction may dependon the distribution cable construction and/or cable characteristics suchas the degree of optical fiber coupling within the cable. In otherwords, some cable designs are better suited for free pass-through, whileother cable configurations are better suited for the demarcation point.Additionally, the transition tube may used with the demarcation point ifdistribution optical fiber is generally fixed by a material, therebycreating a demarcation point.

As depicted, cap 64 includes an opening 64 a that is sized for receivingtransition tube 62 therethrough such as round, rectangular, etc. Afterdistribution optical fibers 32 are routed through first access location38 a to extend beyond protective covering 38, transition tube 62 is slidover the distribution optical fibers 32 and may be pushed into a portionof distribution cable 30 as shown in FIG. 6 e. In other words,transition tube 62 protects and routes distribution optical fibers asthey transition from a position within the distribution cable to aposition outside the distribution cable while allowing some movement.Then, the exposed end of transition tube 62 is routed through opening 64a of cap 64 so transition tube 62 extends therefrom as represented bythe dotted line in FIG. 6 c. Transition tube 62 is formed from asuitable material that is flexible, but may also be formed from arelatively rigid material. By way of example, transition tube 62 is aPTFE tube (i.e., a Teflon® tube) that is able to withstand theapplication of high temperatures. In another embodiment, the PTFEtransition tube is chemically etched. Likewise, cap 64 is formed from asuitable material such as PTFE or other flexible material, but cap 64may also be formed from a relatively rigid material. Further, caps forclosing the access location can have other configurations. FIG. 6 hshows a cap 64′ using a notch (not numbered) as the opening for routingthe transition tube and/or optical fiber outward of the protectivecovering. In other words, the distribution optical fiber and/ortransition tube pass through notch of cap 64′ and a portion of theaccess location. Of course, other kits of parts can include othercomponents such as tools for cutting distribution optical fibers, tethertubes, indexing tubes, shrink tubing, sealing components, plugs and/orpreconnectorized pigtails that may include ferrules, receptacles,connector bodies or the like. Likewise, other distribution cableassemblies of the present invention may include other components orsteps as discussed herein.

As depicted in FIG. 6 e, cap 64 is larger than the opening of the accesslocation AL (i.e., longer) and is disposed so that a portion of the sameextends under protective covering 38. Additionally, cap 64 may berelatively thin and flexible so that it is easily tucked underprotective covering 38 by the craft. By way of example, cap 64 is sizedso that about 5 millimeters of cap 64 is disposed under protectivecovering 38 at the ends and has a thickness of about 0.3 millimeters.After cap 64 is in position, a step of securing the same using amaterial 66 may be performed as depicted in FIG. 6 f. In thisembodiment, material 66 is a hot melt adhesive available from Loctiteunder the tradename Hysol 83245-232, but any suitable material or methodmay be used for securing the cap such as a glue, adhesive, silicone,sonic welding or the like as long as the material used is compatiblewith the optical fiber, ribbons, protective covering, and/or othercomponents that it may contact. Additionally, cap 64 and/or material 66may also function to inhibit any optional sealing material such as anovermolded sealing material from entering the distribution cable.Furthermore, it is possible to apply material 66 below cap 64.

Of course cap 64 can have other suitable configurations and can varybased on the distribution cable. For instance, cap 64 can be shaped ortailored to match the profile of the portion of the protective covering38 that is removed from the distribution cable. In other words, the caphas a length and width to match the length and width of the opening ofthe first access location along with an inner and outer profile to matchthe protective covering profile of the section that was removed.Consequently, the cap closes the first access location with a generallyflush surface. As an example, a generally round distribution cablejacket would use a cap having a similar inner and outer radius as thecable jacket with a suitable arc length, longitudinal length, and widthto match the access location opening. FIG. 6 d shows a cross-sectionalview of cap 64 shaped for closing the access location of a generallyround distribution cable, but other shapes, profiles, and/or lengths ofthe cap are possible to tailor the cap to fit other cables and/oropenings. Additionally, cap 64 may be attached at the first accesslocation 38 a using a suitable material or method such as an adhesive,glue, sonic welding, or the like.

As discussed, the method of flowchart 40 requires selecting at least oneoptical fiber of the plurality of optical fibers of the distributioncable as a distribution optical fiber. Distribution cables can have anysuitable arrangement and/or type of optical fibers therein and theconcepts of the invention are useful with the different arrangementsand/or types of optical fibers. For instance, the present invention issuitable with cables having bare optical fibers (e.g., the strandedloose tube cable of FIG. 3 a) and cables having one or more ribbons(e.g., the slotted core cable of FIG. 3 b, the monotube cable of FIG. 3c, or the flat ribbon cable of FIG. 3 d). Still other distributioncables may have buffered optical fibers (FIG. 3 e), bundles of opticalfibers, or the like. Distribution cables having buffered optical fibersmay require more force on the cutting element to severe the buffer layerand the optical fiber but are within the scope of the present invention.After the optical fibers for distribution are selected, a dividing tool(not shown) such as a thin piece of metal or plastic may be used at theaccess location for separating the selected optical fibers from theremaining portion of the distribution cable.

In cables using ribbons, it may be desirable to select less than all ofthe optical fibers of a ribbon as distribution optical fibers. By way ofexample, four distribution optical fibers may be desired at an accesslocation and each ribbon of the distribution cable has twelve opticalfibers. As shown in FIG. 6 g, a ribbon R has a split S formed by thecraft between the fourth and fifth optical fibers of ribbon R for ashort distance near the access location. Thus, the desired opticalfibers for distribution are segregated for splitting ribbon R along itslongitudinal length before cutting the same. More specifically, FIG. 6 gshows that cutting element 58 of tool 50 is then looped about the foursegregated optical fibers of split ribbon R and tool 50 is positioned asbefore. Thereafter, the split S in the ribbon is propagated along itslongitudinal length by the tool within the distribution cable. In otherwords, as tool 50 is slid within the distribution cable to the cuttinglocation CL as before, cutting element 58 splits the ribbon along itslongitudinal length by shearing the matrix material of the ribbonbetween the desired optical fibers as tool 50 is slid into position tothe cutting location. Thereafter, the selected distribution opticalfiber(s) is severed as before using the tool.

As discussed above, the distribution optical fiber can be generallyfixed for inhibiting movement. FIG. 6 i depicts a distribution cable 30′having a demarcation point 80 for generally inhibiting the movement ofthe distribution optical fiber 32′ at or near the access location.Generally speaking, demarcation point 80 fixes the distribution opticalfiber near the access location for inhibiting movement of the same toreduce undue stresses on the distribution optical fiber such as duringbending, thereby preserving optical performance. One method forproviding demarcation point 80 is by applying or injecting a suitablematerial about the distribution optical fiber 32′ at the accesslocation. For instance, the demarcation material may be applied and/orinjected into the distribution cable about the distribution opticalfiber, thereby inhibiting the movement of the distribution opticalfiber. Any suitable material may be used for the demarcation point suchas a hot melt adhesive, silicone, or the like disposed about thedistribution optical fiber. However, the material used for demarcationshould be compatible with the optical fiber, ribbons, protectivecovering, and/or other components that it may contact. Additionally,demarcation point 80 may be used with or without a cap 64′ and may bedisposed inward or outward of the cap if used. If the cap is omitted,demarcation point 80 may also function to inhibit any optional sealingmaterial such as an overmolded sealing material from entering thedistribution cable.

Additionally, concepts of the present invention can be practiced withoutcutting the distribution optical fiber from within the distributioncable. For instance, FIG. 6 i depicts a generic distribution cable 30′having a first and second opening 38 a′,38 b′ in protective covering38′. In other words, the demarcation point 80 is used with aconventional access method where the cable is opened in two locations 38a′ and 38 b′ for obtaining the desired length of distribution opticalfiber. Additionally, one or more of openings 38 a′, 38 b′ can be closedwith suitable a cap 64′ as depicted. Likewise, the method of providingexcess fiber length for the distribution optical fiber by indexing asdiscussed below can be performed without cutting the distributionoptical fiber from within the distribution cable.

FIGS. 7 and 8 respectively are a perspective and an exploded view and ofa specific explanatory fiber optic distribution cable assembly 100(hereinafter cable assembly 100) according to the present invention. Asbest shown in FIG. 8, distribution cable assembly 100 includes adistribution cable 110, a distribution optical fiber pigtail 115′, a cap120 for access location AL, a transition tube 130, a tether tube 140, anindexing tube 150, an indexing tube plug 160, a splice protector 170, aheat shrink tube 180, and a sealing portion 190. FIGS. 9-11 arecross-sectional views of assembly 100 respectively taken along line 9-9,line 10-10, and line 11-11. Additionally, FIGS. 10 and 10 a are shownwith the cavity of the distribution cable empty for clarity purposes.Cable assembly 100 includes indexing tube 150 so that a predeterminedamount of excess ribbon length (ERL) or excess fiber length (EFL) can beloaded into the distribution optical fiber as will be discussed. LoadingERL or EFL into the distribution optical fibers inhibits stresses on thesame such as during bending of the cable assembly. Additionally, cableassembly 100 is one example of many different distribution cablesaccording to the present invention that may include fewer or morecomponents, components having different configurations, differentarrangement of components, or the like.

FIG. 9 depicts that both distribution fiber optic cable 110 and tethertube 140 have a generally non-round cross-section such as a generallyflat shape, thereby allowing a relatively small overall cross-sectionaldimension for assembly 100. In other words, flat portions ofdistribution cable 110 and tether tube 140 are generally aligned toallow a small footprint compared with using two round cables. By way ofexample, distribution cable assembly 100 and other similar assembliescan have a cross-sectional maximum dimension MD as shown in FIG. 11,which is along a diagonal. Cross-sectional maximum dimension MD can varybased on the size of the components used, but in embodimentsadvantageous for duct specific applications the cross-sectional maximumdimension is about 30 millimeters or less, more preferably about 28millimeters or less, and most preferably about 25 millimeters or less,thereby allowing the pulling of the cable assembly into the duct. Ofcourse, other embodiments can have other larger or smallercross-sectional maximum dimensions for the given application.

Distribution cable 10 is advantageous for several reasons, but the useof other distribution cables is possible. First, distribution cable 110and other similar distribution cables are advantageous since they canhave a relatively high optical waveguide count with a relatively smallcross-sectional footprint. By way of example, distribution cable 110 hasfour ribbons each having twenty-four optical fibers for a total fibercount of ninety-six fibers. With twenty-four fiber count ribbons,distribution cable 110 has a major cable dimension W of about 15millimeters or less and a minor cable dimension H of about 8 millimetersor less. Second, distribution cable 110 is easily accessed from eitherof the generally planar surfaces (e.g., top or bottom) of the cable sothat the craft is able to access to any optical fiber desired fordistribution. Third, distribution cable 110 allows quick and reliableaccess while inhibiting damage to the optical fibers or strength membersduring the access procedure. In other words, the craftsman can simplycut into the protective covering, thereby gaining access to the cablecavity having the optical fibers therein. Also, in this embodiment,distribution cable 110 has a dry construction (i.e., the cable excludesa grease or gel for water-blocking), thus the craft does not have toclean or remove grease or gels from the optical fibers, ribbons, tools,etc.

Of course, distribution cables according to the present invention mayhave any suitable dimensions, constructions, and/or fiber counts for thegiven application. By way of example, other distribution cables caninclude other components and/or structures for water-blocking such asgrease, gel, extruded foams, silicones, or other suitable water-blockingcomponents. Additionally, suitable water blocking structures may also beintermittent disposed along the distribution cable. Likewise, otherdistribution cables can have other suitable cable components such asarmor, ripcords, or tubes. For instance, another embodiment of thedistribution cable may have a toneable portion for locating the cable inburied applications.

As depicted in FIG. 9, distribution cable 110 includes a plurality ofoptical fibers 112 and a protective covering 118. In this embodiment,distribution cable 110 is a tubeless design having a cavity 111 forhousing a plurality of optical fibers 112, which are configured as aplurality of ribbons 113 (represented by the horizontal lines) arrangedin a non-stranded stack. Distribution cable 110 also includes strengthmembers 114 and water-swellable components 116. As depicted, strengthmembers 114 are disposed on opposite sides of cavity 111 and impart apreferential bend characteristic to distribution cable 110. Strengthmembers 114 provide tensile and/or anti-buckling strength to thedistribution cable and may be formed from any suitable materials such asdielectrics, conductors, composites or the like. Illustratively,strength member 14 are a round glass-reinforced plastic (grp) having adiameter of about 2.3 millimeters, which is smaller than the height ofcavity 111. Of course, strength members 14 can have shapes other thanround such as oval strength members.

Using water-swellable components 116 allows for a dry construction ofdistribution cable 110. Water-swellable components 116 can have anysuitable form such as water-blocking yarn, thread, tape or the like. Inthis case, distribution cable 110 uses two water-swellable components116 configured as elongate tapes that are paid-off reels. As depicted,the major (e.g. planar) surfaces (not numbered) of water swellablecomponents 116 are generally aligned with the major (e.g. horizontal)surfaces (not numbered) of cavity 111, thereby allowing a compact andefficient configuration while generally inhibiting corner optical fibercontact as occurs with a ribbon stack disposed in a round tube.Moreover, the ribbons are generally aligned with a major surface (i.e.the horizontal surface) of the cavity 111 at the top and bottom and alsogenerally aligned with the width (i.e. major surfaces) of thewater-swellable components 116, thereby forming a ribbon/water-swellablecomponent composite stack within cavity 111. Consequently, therectangular (or square) ribbon stack is fitted to a correspondinggenerally rectangular (or square) cavity and avoids the issuesassociated with placing a rectangular (or square) ribbon stack within around buffer tube (i.e. stresses on the corner fibers of the ribbonstack in a round buffer tube that can cause the cable to fail opticalperformance requirements such as bending).

More specifically, water-swellable components 116 are disposed on thetop and bottom of the ribbon stack (not numbered) and include acompressible layer 116 a and a water-swellable layer 116 b. In otherwords, water-swellable components 116 sandwich the plurality of ribbons113 of the non-stranded stack, thereby forming a cable core.Consequently, the ribbon(s) 113, major surfaces of water-swellablecomponents 116, and major (horizontal) surfaces of cavity 111 aregenerally aligned (i.e., generally parallel) to create a compactstructure. Additionally, water-swellable components 116 contact at leasta portion of respective the top or bottom ribbons. In other embodiments,one or more elongate tapes may be wrapped about the optical fibers ordisposed on one or more sides thereof. By way of example, compressiblelayer 116 a is a foam layer such as open cell polyurethane material andwater-swellable layer 116 b is a water-swellable tape. However, othersuitable materials are possible for the compressible layer and/orwater-swellable layer or portion. As shown, compressible layer 116 a andwater-swellable layer 116 b are attached together, but they may beapplied as individual components. Generally speaking, water-swellablecomponent 116 is multi-functional since it provides a degree of couplingfor the ribbons 113, inhibits the migration of water along cavity 111,cushions the ribbons/optical fibers, and allows movement and separationof the ribbons (or optical fibers) to accommodate bending ofdistribution cable 110. In other embodiments, distribution cables mayuse other cable components disposed within the cavity 111 for couplingthe optical fibers, cushioning the optical fibers, and/orwater-blocking. For instance, distribution cables may use a foam tapesor extruded foam that does not include a water-blocking characteristic.

As depicted, cavity 111 has a generally rectangular shape with a fixedorientation to accommodate the non-stranded ribbon stack, but othershapes and arrangements of the cavity are possible such as generallysquare, round, or oval. By way of example, cavity may be rotated orstranded in any suitable manner along its longitudinal length. Thecavity can also have a partial oscillation through a given angle, forinstance, the cavity can rotate between a clockwise angle that is lessthan a full rotation and then rotate counter-clockwise for less than afull rotation. Furthermore, cavity 111 may be offset towards one of theplanar surfaces of distribution cable 110, thereby allowing easy openingand access from one side.

Ribbons 113 used in distribution cable 110 can have any suitable designor ribbon count. For instance, ribbons 113 can have a splittableconstruction using one or more subunits or stress concentration as knownin the art, thereby allowing separation of the ribbon into smallergroups of optical fibers. For instance, a ribbon may use subunits eachhaving four optical fibers; however, ribbons without subunits arepossible and subunits may have different fiber counts. Subunits allowpredetermined splitting of the optical fiber ribbons into predictablesmaller fiber count units before splitting along its length with tool50. In one embodiment, each of the depicted ribbons 113 includes sixfour-fiber subunits for a total of twenty-four optical fibers. Ofcourse, other numbers of optical fibers per ribbon, number of ribbons,and/or other suitable subunit configurations are possible such as twotwelve fiber units, three eight fiber units, or six four fiber unitsdepending on the requirements of the network architecture. Examples ofsuitable optical fiber arrangements include ribbons with or withoutsubunits, ruggedized ribbons having a tight-buffer layer, tight-bufferedor colored optical fibers, loose optical fibers in a tube, opticalfibers in a module, or optical fibers disposed in a bundle.

Additionally, ribbons 113 of this explanatory embodiment of distributioncable 110 have an excess ribbon length (ERL) of about 0.5% or more suchas in range of about 0.6% to about 0.8% to accommodate bending and/orcoiling of distribution cable 110, but the amount of ERL used may varybased on the specific cable design. The ERL of ribbons 113 is related tothe ERL of the ribbons within the cable and is different than theloading of ERL in the distribution optical fiber using the indexing tubeas briefly discussed above. The minimum bend radius of the distributioncable 110 is about 125 millimeters which allows the cable to be coiledin a relatively small diameter for slack storage. Of course,distribution cables with other suitable fiber/ribbon counts may haveother ERL values and/or cable dimensions. Illustratively, cables similarto distribution cable 110 could have four ribbons with different fibercounts such as: (1) twelve fiber ribbons with a major cable dimension Wof about 12 millimeters or less for a total of forty-eight opticalfibers; (2) thirty-six fiber ribbons with a major cable dimension W ofabout 18 millimeters or less for a total of one-hundred and forty-fouroptical fibers; or (3) forty-eight fiber ribbons with a major cabledimension W of about 21 millimeters or less for a total of two-hundredand sixteen optical fibers.

Additionally, cavity 111 has a cavity height CH and a cavity width CWsuitable for the desired arrangement of optical fibers, ribbon, or thelike. By way of example, each ribbon 113 has a height of about 0.3millimeters for a total ribbon height of about 1.2 millimeters (4 times0.3 millimeters) and the cavity height CH is about 5.5 millimeters forcavity 111. Cavity width CW is generally determined by the width of theribbons (or number of optical fibers) intended for the cable and wouldbe about 7.5 millimeters for the twenty-four fiber ribbons. In thisembodiment, water-swellable components 116 each have an uncompressedheight of about 1.8 millimeters, but other suitable uncompressed heightsare possible. The compression of water-swellable components 116 in thecable is the localized maximum compression of the same and generallyoccurs where the ribbon or ribbon stack has the maximum displacementfrom the neutral axis if the cable includes a positive ERL (i.e., theribbons undulate within the cavity).

Illustratively, the explanatory embodiment has a total height for theuncompressed water-swellable components 116 and ribbon 113 of about 4.8millimeters, which is less than the cavity height CH of 5.5 millimeters.Consequently, a normalized ribbon pullout force is generally caused bythe undulating ribbon stack causing localized maximum compression of thewater-swellable components 116 due to the ERL and/or friction. By way ofexample, proper coupling of the ribbon stack (or ribbons or opticalfibers) may be achieved when the combined uncompressed height of the dryinserts is about 40% or more of the cavity height CH such as by usingtwo 1 millimeter water-swellable components 116 within a cavity having acavity height CH of about 5 millimeters. Of course, other suitableratios are possible as long as optical performance is preserved. In theexplanatory embodiment, the combined uncompressed height (2 times 1.8millimeters equals 3.6 millimeters) of water-swellable components 116 isabout 65% of the cavity height CH (5.5 millimeters), which is more than50% of the cavity height CH. Of course, the cavity, ribbons, and/orwater-swellable components 116 can have other suitable dimensions whilestill providing suitable performance. For instance, thinner ribbonsand/or water-swellable components may be used. Although cavity 111 isdepicted as rectangular it may be difficult to make a rectangular cavityas shown, i.e., the extrusion process may create the cavity with asomewhat irregular rectangular shape. Likewise, the cavity can haveother suitable shapes besides generally rectangular such as oval, roundor the like, which may generally change the relationship (alignment)among the dry insert, ribbon, and/or cavity.

Generally speaking, positioning water-swellable components 116 onopposite ends of the ribbon stack (or single ribbon or loose opticalfibers) aids in influencing and maintaining a generally uniform ERLdistribution along distribution cable 110 during different conditions,thereby helping to preserve optical performance. Moreover, ribbon tocable coupling is beneficial for influencing a relatively even ERLdistribution along the cable such as during bending, which generallyallows for small cable bend radii. Other factors such as the size ofcavity and/or compression of the dry insert(s) may also influenceERL/EFL distribution along the cable.

Another optical performance aspect of distribution cables having agenerally flat profile with a non-stranded ribbon stack is the totalamount of ERL required for suitable cable performance. The amount of ERLfor adequate cable performance generally depends on the cable designsuch as the number of ribbons. Generally speaking, the minimum ERL forcables having a single ribbon is determined by the desired allowablelevel of fiber strain at the rated cable load; whereas, the minimum ERLfor a multiple ribbon cable is generally influenced by bendingperformance. More specifically, when selecting the minimum ERL limit fora cable design the strength member geometry and material (i.e.cross-sectional area and Young's modulus) should be considered forcalculating the desired level of fiber strain at the rated tensile loadof the cable design. Additionally, the amount of ERL required forbending generally increases as the number of ribbons in the stackincreases since the outer ribbons of the ribbon stack are farther fromthe neutral axis of the cable. However, there are limits on the upperend of ERL for suitable optical performance (i.e. too much ERL candegrade optical performance). Furthermore, distribution cables havingrelatively high levels of ERL such as in the range of 0.6% to 1.5% maybe suitable for self-supporting installations such as NESC heavyloading, but the particular ERL for a given design should have thedesired cable performance. On the other hand, distribution cablessimilar to distribution cable 110 having loose optical fibers may havelower values of excess fiber length (EFL) such as about 0.2% EFL sinceall the optical fibers are located near the neutral axis of the cable.

Returning to cable assembly 100, FIGS. 12-16 depict perspective viewsshowing portions of distribution cable 110 in various stages ofconstruction (i.e., subassemblies) for explaining the method of makingcable assembly 100. FIG. 12 depicts distribution cable 110 after accesslocation AL is made in protective covering 118 and distribution opticalfibers 115 are cut within distribution cable 110 and routed through theopening at access location AL with cap 120 and transition tube 130installed, thereby forming a subassembly 102 of cable assembly 100. Fromsubassembly 102, a variety of distribution cables may be constructedsuch as cable assembly 100 shown in FIGS. 7 and 8 or a cable assembly200 as shown in FIGS. 17 and 18. Furthermore, subassembly 102 or othersubassembly constructions are suitable for deployment in the field.Simply stated, the distribution optical fibers of subassembly 102 arepresented outside of the distribution cable for use by the craft in thefield. If used in this manner, a tape or other covering may be disposedabout the distribution optical fibers and/or access location forprotecting the same until access is needed in the field.

Subassembly 102 is formed as described below. First, protective covering118 of distribution cable 110 about access location AL is roughened byscalloping and/or flame brushing as shown. Roughening protectivecovering 118 improves the adhesion of sealing portion 190 with the sameand is easier and safer to accomplish before opening protective covering118. Thereafter, an opening 118 a of access location AL is made inprotective covering 118. Opening 118 a may be any suitable length and inthis case is about 25 millimeters long. Any suitable cable entry toolmay be used for opening protective covering 118 such as a utility knifeor the like. After opening protective covering 118, a portion of the topwater-swellable component 116 of distribution cable 110 is exposed ataccess location AL. The exposed portion of water-swellable component 116is removed such as by cutting with a scissors, thereby allowing foreasier access to the optical fibers within distribution cable 110.Thereafter, the desired optical fibers for distribution are selected forcutting within the distribution cable and special tools such as thedividing tool may be used. In this example, less than all of the opticalfibers of the top ribbon are selected for distribution so the top ribbonincludes split S between optical fibers like depicted in FIG. 6 f.Specifically, four optical fibers of the top ribbon are selected tobecome distribution optical fibers at access location AL. Of course,optical fibers from other ribbons in the stack may be selected fordistribution. Additionally, if the ribbon(s) above the ribbon beingaccessed have already been used, the used ribbons may be removed foraccess to the desired optical fibers for distribution. Split S in thetop ribbon is made by the craft using a suitable tool and/or theirfingers. Thereafter, cutting element 58 of tool 50 is positioned aboutsplit S like depicted in FIG. 6 f. Then, the slack of cutting element 58is taken up and tool 50 is slid into cavity 111 of distribution cable110, thereby splitting the ribbon between optical fibers along itslongitudinal length as tool 50 moves into position. After tool 50 ispositioned at the cutting location CL within distribution cable 110cutting element 58 is pulled with sufficient force to cut distributionoptical fibers 115 within distribution cable 110.

In this case, tool 50 is inserted so as to cut distribution opticalfibers 115 about 175 millimeters downstream from access location AL.Consequently, the distribution optical fiber length DOFL is about seven(7) times longer than the access length AL. After tool 50 is removedfrom distribution cable 110, distribution optical fibers 115 are pulledout of cavity 111 and presented outward of protective covering 118.Next, cap 120 (which is similar to cap 64) and transition tube 130(which is similar to transition tube 62) that are sized and shaped fordistribution cable 110 with its access location AL are installed likeshown in FIG. 6 e. More specifically, transition tube 130 has a lengthof about 65 millimeters and a generally rectangular shape for slidingover optical fibers split from optical fiber ribbon 113 and cap 120 isgenerally flat and has a length that is slightly longer than accesslocation AL so that a portion may fit within cavity 111 of distributioncable 110. Transition tube 130 is slid over distribution optical fibers115 so that about 35 millimeters is disposed within cavity 111 ofdistribution cable 110. Then, the exposed end of and transition tube 130is routed through an opening 120 a of cap 120 and cap 120 is positionedso that a portion of the same is tucked into cavity 111 of distributioncable 110. As before, cap 120 closes access location AL and transitiontube 130 protects distribution optical fibers 115 as they are routed outof distribution cable 110. Thereafter, a material (not shown) such as ahot melt adhesive is applied above cap 120 and about transition tube 130for securing cap 120 and transition tube 130 at the opening of theaccess location like as shown in FIG. 6 f.

FIG. 13 depicts a perspective view of another subassembly 104 of cableassembly 100 for explaining the method of making. More specifically,FIG. 13 shows subassembly 102 of FIG. 12 after splicing distributionoptical fiber 115 with distribution optical fiber pigtail 115′ andprotecting the splice location with splice protector 170. For thisembodiment and access location of cable assembly 100, the distributionoptical fiber pigtail 115′ is a four fiber ribbon that is mass fusionspliced with the distribution optical fibers 115 that were split out ofthe top ribbon. In other words, distribution optical fiber pigtail 115′is in optical communication with distribution optical fiber 115 andbecomes part of the same. Moreover, this step increases the length ofthe distribution optical fiber based upon the desired connectivityconfiguration such as the length of the tether tube or otherconfigurations. Splice protector 170 is used for protecting andimmobilizing the splice (not visible) and may be pushed ontodistribution optical fiber pigtail 115′ before splicing and thenpositioned over the splice after it is made. Likewise other componentsmay be slid over distribution optical fiber pigtail 115′ depending onthe configuration of the embodiment. Like subassembly 102, a variety ofdistribution cables may be constructed from subassembly 104 or othersimilar subassemblies. Cable assembly 100 includes tether tube 140 witha distribution optical fiber stub (the second end of distributionoptical fiber pigtail 115′) for optical connectivity, but otherconfigurations are possible. For instance, the second end of thedistribution optical fiber 115′ can have one or more ferrules attachedthereto and the ferrule may be a portion of a receptacle, plug, or thelike for plug and play connectivity. As an example, FIG. 19 depicts asecond end of tether tube 140′ having the distribution optical fiberattached to a ferrule that is a portion of plug 195 as known in the art.Of course, the second end of tether tube 140′ can have any suitableconfiguration for connectivity such as splice-ready optical fibers, aconnector or a receptacle having a ferrule, a multi-port or the like,thereby allowing the craft flexibility for downstream connectivity.Illustratively, FIG. 19 a depicts distribution optical fibers 115′attached to a ferrule 196. Ferrule 196 is a multifiber ferrule, butsingle fiber ferrules may be attached to one or more distributionoptical fibers. FIG. 19 b depicts a multi-port 198 having a plurality ofreceptacles 198 a attached to the end of tether tube 140. Likewise, FIG.19 c depicts another multi-port 199 having a plurality of receptacles199 a attached to the end of tether tube 140. FIGS. 19 d and 19 edepicts a branching of tether tube using furcation legs for providingplug and play connectivity. More specifically, FIG. 19 d shows assembly193 having a plurality of plugs 193 a disposed on the ends of aplurality of furcation legs 193 b and FIG. 19 e shows assembly 194having a plurality of receptacles 194 a disposed on the ends of aplurality of furcation legs 194 b. Of course, other types and/orstructures are possible for optical connectivity such as singlereceptacle or the like. As explained below, cable assembly 100 has thesplice disposed within the cavity of indexing tube 150 as will beexplained below for protecting the splice and loading an ERL or EFL intothe distribution optical fiber.

As best shown in FIG. 10 a, splicing indexing tube 150 is slid over aportion of distribution optical fiber 115 and a portion of transitiontube 130. Consequently, splice protector 170 is disposed within a cavity150 a of indexing tube 150 and fiber pigtail 115′ extends from a secondend of indexing tube 150. Furthermore, splice 170 can have an optionalcushioning element (not shown) such as a foam tape disposed thereabout.For instance, the foam can be positioned about splice 170 such as foldedover the same before indexing tube 150 is slid thereover. As furthershown, indexing tube plug 160 is then pushed into the upstream end ofindexing tube 150. Indexing tube plug 160 is used for inhibiting sealingportion 190 from being injected into indexing tube 150 in a furthermanufacturing process. Indexing tube plug 160 may be formed from anysuitable material such as a foam, soft polymer, or the like and is sizedfor fitting into the cavity of the indexing tube 150 along withtransition tube 130 as a light friction fit. Then, if desired, indexingtube 150 may be taped or secured to distribution cable 110 for holdingthe same in place at a suitable position. In this embodiment, indexingtube 150 is a portion of distribution cable 110 having an empty cavityas best shown by FIG. 11. In other words, indexing tube 150 is a portionof distribution cable 110 with the ribbons 113 and water-swellablecomponents 116 removed from cavity 111 (i.e., just the protectivecovering 118 having strength members 114 embedded therein). Of course,the use of other suitable indexing tubes having other sizes and/orshapes such as round, square, etc is possible.

FIG. 14 depicts a perspective view of a subassembly 106 of cableassembly 100 disposed within a mold 192 as shown by the phantom linesbefore injecting a curable material for forming the sealing portion 190.Subassembly 106 further includes a step of applying a material 106 asuch as a hot melt adhesive for sealing and/or securing components ofthe assembly together such as fixing the position of transition tube130. Applying material 106 a inhibits the injected material fromentering the opening of the access location, indexing tube 150, and/orfrom moving components during the overmolding process, therebypreserving optical performance. Additionally, it may be beneficial toheat up a portion of subassembly 106 shortly before forming sealingportion 190 therearound to promote bonding of sealing portion 190 withsubassembly 106. Thereafter, subassembly 106 is placed into mold 192 asshown in FIG. 14 and sealing portion 190 is formed by injecting thesealing material into the mold under pressure. Sealing portion 190provides environment protection for the access location AL and mayprovide structural integrity. In this embodiment, sealing portion 190 isa 2-part material formed of isocyanate resin and polyol hardeneravailable from Loctite. In this embodiment, sealing portion 190 has agenerally uniform minimum wall thickness of about 3-5 millimeters, butother dimensions are possible. Other methods and/or materials for makingsealing portion 190 are possible so long as they meet the requirementsof the desired application. Sealing portion 190 can be formed bytechniques or manufacturing methods other than by injecting a curablematerial into a mold. For example, FIG. 20 depicts a sealing portion190′ that is a preformed shell that fits over subassembly 106 and thenhas heat (or other reactions) for partially or totally melting and/orforming the same, thereby sealing the access location. Morespecifically, sealing portion 190′ has a hinge line 192′ for allowingthe same to be folded about subassembly 106. In other embodiments,sealing portion 190′ can be two or more separate portions. Sealingportions such as sealing portions 190′ can be used with any suitabledistribution cable. By way of example, FIGS. 20 a-c depict the use of analternative sealing portion 190″ with a distribution cable 110′ andtether tube 140′ that have round cross-sections, thereby forming cableassembly 100′. In still further embodiments, a ruggedized tubing (notshown) may be placed about the access location and then injected with asuitable material for sealing the ends or the entire ruggedized tubing.If the application allows, sealing portion 190 may also be formed usinga heat shrink tubing disposed about the access location.

FIG. 15 depicts a perspective view of a subassembly 108 of cableassembly 100 before tether tube 140 is indexed with respect to indexingtube 150. More specifically, indexing tether tube 140 into and relativeto indexing tube 150 enables the loading a predetermined amount of ERLinto distribution optical fiber 115 and/or distribution optical fiberpigtail 115′. Consequently, the ERL or EFL of the distribution opticalfiber inhibits forces from being applied to the same that may causereliability and/or optical attenuation issues. As best depicted in FIG.10, cavity 150 a of indexing tube 150 is sized so that tether tube 140fits into the same. FIG. 9 shows that tether tube 140 includes aplurality of strength members 142 disposed on opposite sides of a cavity141 and houses a portion of distribution optical fiber 115′ therein.Tether tube 140 has a generally flat shape, but other sizes and/orshapes of tether tube may be used with the concepts of the presentinvention. FIG. 15 shows tether tube 140 disposed within a portion ofindexing tube 150 and pulled taut for removing excess ribbon length asrepresented by mark M1. Thereafter, tether tube 140 is pushed (i.e.,indexed) into indexing tube 150 a predetermined distance D representedby mark M2. In this cable assembly, distance D is about 5 millimeters,thus an ERL of about 5 millimeters is introduced into the distributionoptical fiber that generally speaking accumulates within the indexingtube 150. Of course, other suitable distances D may be used for loadingthe desired ERL or EFL. After indexing occurs tether tube 140 needs tobe fixed in position for maintaining the ERL or EFL. As shown in FIG. 7heat shrink tubing 180 is applied over a portion of tether tube 140 anda portion of indexing tube 150 for maintaining the relative positions,but other methods are possible for maintaining relative positions suchas overmolding or the like. Additionally, it should be understood thatthe method of indexing a first tube with a second tube for providing ERLor EFL may be used without the step of cutting the distribution opticalfiber within the distribution cable. Of course, other variations arepossible for cable assembly 100. By way of example, FIG. 16 depictscable assembly 100 having an optional cable tie 196 for securingdistribution cable 110 and sealing portion 190 near the downstream end,thereby inhibiting a separation force between the two.

As discussed above, subassemblies of the present invention may beconstructed into other cable assembly configurations. By way of example,FIGS. 17 and 18 depicts cable assembly 200 which includes subassembly102 having a distribution optical fiber pigtail 115′ spliced thereto andprotected by a splice protector 270. As best shown in FIG. 18,distribution optical fiber pigtail 115′ includes a ferrule (not visible)attached thereto. In this embodiment, the ferrule is a multifiberferrule. Moreover, the ferrule is a portion of a connector body 220,thereby providing plug and play optical connectivity at the accesslocation, instead of at the end of the tether tube.

Of course, cable assemblies 100 and 200 are examples of a multitude ofdistribution cables made according the concepts of the disclosure. Asdiscussed, other assemblies could use other cable cross-sections or havefewer, more, and/or different components. By way of example, the sealingportion 190 of distribution cable 100 may include a segmented end 190 aas shown by the phantom lines in FIG. 7. Segmented end 190 a allows somestrain relief for the leading end of the distribution location.Additionally, cable assemblies of the present invention can includeother components such as for aiding the installation of the same into aduct. By way of example, FIG. 21 depicts a distribution cable 300 havinga pulling safety device 302 disposed ahead of the access location asdepicted. More specifically, pulling safety device 302 allows the craftto detect blockages and/or constrictions in a duct so that the craftdoes not damage the access location trying to pull the distributioncable past the blockage or constriction in the duct. In this embodiment,safety pulling device is sized to be slightly larger than the sealingportion 190, thereby allowing the craft to sense an increased forceand/or damage pulling safety device 302 before reaching the accesslocation. Of course, the safety pulling device could have a size and/orshape that is similar or the same as the sealing portion. Consequently,the craft can pull the distribution cable out of the duct beforedamaging the same and repair or clear the duct before trying toreinstall the distribution cable. In other embodiments, safety pullingdevice can be shaped to promote twisting or alignment of thedistribution cable to fit past the blockage or constriction.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Forinstance, the concepts described herein can be applied to any suitablefiber optic cable designs. Likewise, fiber optic cables may includeother suitable cable components such as ripcords or the like or othercomponents for optical connectivity. Thus it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

We claim:
 1. A fiber optic distribution cable comprising: a fiber opticdistribution cable, the fiber optic distribution cable having aplurality of optical fibers and a protective covering; at least onedistribution optical fiber, the at least one distribution optical fiberbeing selected from one of optical fibers of the fiber opticdistribution cable, the at least one distribution optical fiberprotruding from an access location of the protective covering; a sealingportion disposed about the access location; an indexing tube, theindexing tube having a portion secured by the sealing portion andanother portion of the indexing tube extending beyond the sealingportion; and a tether tube, the tether tube being disposed about aportion of the at least one distribution optical fiber for protectingthe at least one distribution optical fiber, wherein the tether tube isattached at a predetermined position relative to the indexing tube,thereby loading an excess fiber length in the distribution opticalfiber.
 2. The fiber optic distribution cable of claim 1, furtherincluding a heat shrink tubing disposed about a portion of the indexingtube for maintaining a relative position between the indexing tube andthe tether tube.
 3. The fiber optic distribution cable of claim 1,wherein the access location has a length AL and the distribution opticalfiber has a distribution optical fiber length DOFL of about 5/4 AL ormore before splicing.
 4. The fiber optic distribution cable of claim 1,the fiber optic distribution cable having a cross-section that isnon-round.
 5. The fiber optic distribution cable of claim 1, the fiberoptic distribution cable having a cross-section that is non-round andthe tether tube having a cross-section that is non-round.
 6. The fiberoptic distribution cable of claim 1, a cross-sectional maximum dimensionof the fiber optic distribution cable being about 30 millimeters orless.
 7. The fiber optic distribution cable of claim 1, furtherincluding a transition tube for the distribution optical fiber.
 8. Thefiber optic distribution cable of claim 1, further including a cap forclosing the access location.
 9. The fiber optic distribution cable ofclaim 1, further including a cap for closing the access location and atransition tube for protecting a portion of the distribution opticalfiber.
 10. The fiber optic distribution cable of claim 1, wherein thedistribution optical fiber is at least one optical fiber of an opticalfiber ribbon.
 11. The fiber optic distribution cable of claim 1, furtherincluding a ferrule attached to the distribution optical fiber foroptical connectivity.
 12. The fiber optic distribution cable of claim 1,further including a tether tube, the tether tube being disposed about aportion of the distribution optical fiber for protecting thedistribution optical fiber and a ferrule attached to the distributionoptical fiber for optical connectivity.
 13. The fiber optic distributioncable of claim 1, wherein the fiber optic distribution cable has a dryconstruction.
 14. The fiber optic distribution cable of claim 1, thefiber optic distribution cable including a non-stranded stack of fiberoptic ribbons.
 15. The fiber optic distribution cable of claim 1, thefiber optic distribution cable including a non-stranded stack of fiberoptic ribbons and a first water-swellable component disposed on a firstside of the non-stranded stack and a second water-swellable componentdisposed on a second side of the non-stranded stack.
 16. The fiber opticdistribution cable of claim 1, further including a plurality of accesslocations.
 17. A fiber optic distribution cable comprising: a fiberoptic distribution cable, the fiber optic distribution cable having aplurality of optical fibers and a protective covering; at least onedistribution optical fiber, the at least one distribution optical fiberbeing selected from one of optical fibers of the fiber opticdistribution cable, the at least one distribution optical fiberprotruding from an access location of the protective covering, whereinthe access location has a length AL and the distribution optical fiberhas a distribution optical fiber length DOFL of about 5/4 AL or morebefore splicing; a sealing portion disposed about the access location;an indexing tube, the at least one distribution optical fiber beingrouted into the indexing tube and having an optical fiber splice thereinfor extending the length at least one distribution optical fiber and aportion of the indexing tube secured by the sealing portion and anotherportion of the indexing tube extending beyond the sealing portion; and atether tube, the tether tube being disposed about a portion of the atleast one distribution optical fiber for protecting the at least onedistribution optical fiber, wherein a portion of the tether tube isdisposed within the indexing tube at a predetermined position relativeto the indexing tube, thereby loading an excess fiber length in thedistribution optical fiber.
 18. The fiber optic distribution cable ofclaim 17, further including a heat shrink tubing disposed about aportion of the indexing tube for maintaining a relative position betweenthe indexing tube and the tether tube.
 19. The fiber optic distributioncable of claim 17, the fiber optic distribution cable having across-section that is non-round.
 20. The fiber optic distribution cableof claim 17, the fiber optic distribution cable having a cross-sectionthat is non-round and the tether tube having a cross-section that isnon-round.
 21. The fiber optic distribution cable of claim 17, across-sectional maximum dimension of the fiber optic distribution cablebeing about 30 millimeters or less.
 22. The fiber optic distributioncable of claim 17, further including a transition tube for thedistribution optical fiber.
 23. The fiber optic distribution cable ofclaim 17, further including a cap for closing the access location. 24.The fiber optic distribution cable of claim 17, further including a capfor closing the access location and a transition tube for protecting aportion of the distribution optical fiber.
 25. The fiber opticdistribution cable of claim 17, wherein the distribution optical fiberis at least one optical fiber of an optical fiber ribbon.
 26. The fiberoptic distribution cable of claim 17, further including a ferruleattached to the distribution optical fiber for optical connectivity. 27.The fiber optic distribution cable of claim 17, wherein the fiber opticdistribution cable has a dry construction.
 28. The fiber opticdistribution cable of claim 17, the fiber optic distribution cableincluding a non-stranded stack of fiber optic ribbons.
 29. The fiberoptic distribution cable of claim 17, the fiber optic distribution cableincluding a non-stranded stack of fiber optic ribbons and a firstwater-swellable component disposed on a first side of the non-strandedstack and a second water-swellable component disposed on a second sideof the non-stranded stack.
 30. The fiber optic distribution cable ofclaim 17, further including a plurality of access locations.